CARPUS. 143 



To ascertain to which hand this bone belongs, hold it so that the base is 

 directed backwards, and the articular facet for the pisiform bone upwards ; the 

 concave articular facet will point to the side to which the bone belongs. 



Articulations. With three bones: the semilunar externally, the pisiform in 

 front, the unciform below, and with the triangular interarticular fibre-cartilage 

 which separates it from the lower end of the ulna. 



The Pisiform bone may be known by its small size, and from its presenting a 

 single articular facet. It is situated at the anterior and inner side of the carpus, 

 is nearly circular in form, and presents on its posterior surface a smooth, oval 

 facet, for articulation with the cuneiform bone. This facet approaches the supe- 

 rior, but not the inferior, border of the bone! Its anterior or palmar surface is 

 rounded and rough, and gives attachment to the anterior annular ligament. The 

 outer and inner surfaces are also rough, the former being convex, the latter usually 

 concave. 



To ascertain to which hand it belongs, hold the bone with its posterior or artic- 

 ular facet downwards, and the non-articular portion of the same surface back- 

 wards ; the inner concave surface will then point to the side to which the bone 

 belongs. 



Articulations. With one bone, the cuneiform. 



Attachment of Muscles. To two : the Flexor carpi ulnaris, and Abductor minimi 

 digiti ; and to the anterior annular ligament. 



BONES OF THE LOWER Eow. (Figs. 94 and 95.) 



The Trapezium is of very irregular form. It may be distinguished by a deep 

 groove, for the tendon of the Flexor carpi radialis muscle. It is situated at the 

 external and inferior part of the carpus, between the scaphoid and first meta- 

 carpal bone. The superior surface, concave and smooth, is directed upwards and 

 inwards, and articulates with the scaphoid. Its inferior surface, directed down- 

 wards and outwards, is oval, concave from side to side, convex from before back- 

 wards, so as to form a saddle-shaped surface, for articulation with the base of the 

 first metacarpal bone. The anterior or palmar surface is narrow and rough. 

 At its upper part is a deep groove, running from above obliquely downwards and 

 inwards; it transmits the tendon of the Flexor carpi radialis, and is bounded 

 externally by a prominent ridge, the oblique ridge of the trapezium. This sur- 

 face gives attachment to the Abductor pollicis, Flexor ossis metacarpi, and Flexor 

 brevis pollicis muscles; and the anterior annular ligament. The posterior or 

 dorsal surface is rough, and the external surface also broad and rough, for the 

 attachment of ligaments. The internal surface presents two articular facets ; the 

 upper one, large and concave, articulates with the trapezoid; the lower one, 

 narrow and flattened, with the base of the second metacarpal bone. 



To ascertain to which hand it belongs, hold the bone with the grooved palmar 

 surface upwards, and the external, broad, non-articular surface backwards; the 

 saddle-shaped surface will then be directed to the side to which the bone belongs. 



Articulations. With four bones : the scaphoid above, the trapezoid and second 

 metacarpal bones internally, the first metacarpal below. 



Attachment of Muscles. Abductor pollicis, Flexor ossis metacarpi, part of the 

 Flexor brevis pollicis, and the anterior annular ligament. 



The Trapezoid is the smallest bone in the second row. It may be known by 

 its wedge-shaped form ; its broad end occupying the dorsal, its narrow end the 

 palmar surface of the hand. Its superior surface, quadrilateral in form, smooth 

 and slightly concave, articulates with the scaphoid. The inferior surface articu- 

 lates with the upper end of the second metacarpal bone ; it is convex from side to 

 side, concave from before backwards, and subdivided, by an elevated ridge, into 

 two unequal lateral facets. The posterior or dorsal, and anterior or palmar 

 surfaces are rough, for the attachment of ligaments ; the former being the larger 

 of the two. The external surface, convex and smooth, articulates with the 



